1. Field of the Invention
This invention relates to a reversible lubricant pump and, more specifically, to such a pump which can be utilized with each of the tandem drive axles of a heavy duty on-highway or off-highway vehicle.
2. Description of the Prior Art
Heretofore, lubrication for each axle of a heavy duty vehicle having tandem drive axles has been provided by splashing oil from an internal oil sump associated with each respective axle. When each axle is driven from a common drive shaft, as is sometimes the case for off-highway applications, this method of lubrication can provide satisfactory results. However, at low speeds, insufficient lubrication for the input axle bearing for each of the forward and rear axles has resulted in some problems.
But, more significantly, an interaxle differential is often employed to allow each axle to operate independently. The interaxle differential has been widely accepted for on-highway applications, and, as a result, additional lubricating problems soon became apparent. Since providing oil by splashing was insufficient for some slow speed operations, it is understandable that the total lack of rotation of a forward axle made possible by the interaxle differential has further proven splash lubrication to be inadequate. With rotation of the drive shaft, without rotation of the forward axle, the input shaft and the interaxle differential, which are located in the forward axle assembly, are forced to rotate.
These general lubricating problems exist whether the vehicle is being operated in a forward or a reverse direction. It is therefore also necessary to provide continuous lubrication independent of the direction of operation of the vehicle.
Although there has been in the past a number of reversible lubricant pumps, such as, for example, those disclosed in U.S. Pat. Nos. 1,717,814, 2,136,318 and 3,852,004, a reversible lubricant pump having improved features for the particular operating environment and working conditions of a heavy duty vehicle with tandem drive axles is desirable.